This research will provide training experience in clinical investigation and epidemiology. The course work will supply the foundation and working closely with a strong mentor on the two study projects will bestow the practical experience needed to become a successful independent investigator. The hypothesis is that Interleukin-16 (IL-16) functions as a disease modifier in asthma. Both study projects are designed to evaluate the prevalence of a single nucleotide polymorphism (SNP) in the IL-16 promoter region in patients with asthma. Additionally, an association between asthma severity and the presence of the SNP in the IL-16 promoter region will be studied. In the first study, 360 affected sib-pair families and 180 hyper-responsive controls were collected. Amplification of genomic DNA to produce PCR products of the IL-16 promoter region will be performed and sent for analysis. The PCR product will be evaluated for the SNP in the IL-16 promoter region. A family linkage analysis on the affected sib-pair families and an association study on the case-controls will be performed. A similar study in the early phase of recruitment will involve 400 asthmatics and 200 controls. The participants DNA will be collected and data on asthma severity will be obtained. An association study to evaluate the prevalence of the SNP in patients with asthma and to look for an association with asthma severity will be done.